During initialization, we override some socket callbacks and set sk_user_data to ovpn_sock. Currently these two operations are decoupled: the callbacks are overridden before sk_user_data is set, leaving a potentially ill-formed state while socket ownership is not yet complete. For example, if a packet arrives after ovpn_udp_socket_attach has been called but before ovpn_socket_new finishes, ovpn_udp_encap_recv may be invoked without a configured sk_user_data pointer.
Set sk_user_data before overriding the callbacks so that it can be accessed safely from them. Since we already check that the socket has no sk_user_data before setting it, this remains safe even if an interrupt accesses the socket after sk_user_data is set but before the callbacks are overridden. Signed-off-by: Ralf Lici <[email protected]> --- drivers/net/ovpn/socket.c | 38 +++++++++++++++++++++----------------- drivers/net/ovpn/tcp.c | 1 + drivers/net/ovpn/udp.c | 1 + 3 files changed, 23 insertions(+), 17 deletions(-) diff --git a/drivers/net/ovpn/socket.c b/drivers/net/ovpn/socket.c index 9750871ab65c..053b8abe5619 100644 --- a/drivers/net/ovpn/socket.c +++ b/drivers/net/ovpn/socket.c @@ -200,6 +200,22 @@ struct ovpn_socket *ovpn_socket_new(struct socket *sock, struct ovpn_peer *peer) ovpn_sock->sk = sk; kref_init(&ovpn_sock->refcount); + /* TCP sockets are per-peer, therefore they are linked to their unique + * peer + */ + if (sk->sk_protocol == IPPROTO_TCP) { + INIT_WORK(&ovpn_sock->tcp_tx_work, ovpn_tcp_tx_work); + ovpn_sock->peer = peer; + ovpn_peer_hold(peer); + } else if (sk->sk_protocol == IPPROTO_UDP) { + /* in UDP we only link the ovpn instance since the socket is + * shared among multiple peers + */ + ovpn_sock->ovpn = peer->ovpn; + netdev_hold(peer->ovpn->dev, &ovpn_sock->dev_tracker, + GFP_KERNEL); + } + /* the newly created ovpn_socket is holding reference to sk, * therefore we increase its refcounter. * @@ -212,29 +228,17 @@ struct ovpn_socket *ovpn_socket_new(struct socket *sock, struct ovpn_peer *peer) ret = ovpn_socket_attach(ovpn_sock, sock, peer); if (ret < 0) { + if (sk->sk_protocol == IPPROTO_TCP) + ovpn_peer_put(peer); + else if (sk->sk_protocol == IPPROTO_UDP) + netdev_put(peer->ovpn->dev, &ovpn_sock->dev_tracker); + sock_put(sk); kfree(ovpn_sock); ovpn_sock = ERR_PTR(ret); goto sock_release; } - /* TCP sockets are per-peer, therefore they are linked to their unique - * peer - */ - if (sk->sk_protocol == IPPROTO_TCP) { - INIT_WORK(&ovpn_sock->tcp_tx_work, ovpn_tcp_tx_work); - ovpn_sock->peer = peer; - ovpn_peer_hold(peer); - } else if (sk->sk_protocol == IPPROTO_UDP) { - /* in UDP we only link the ovpn instance since the socket is - * shared among multiple peers - */ - ovpn_sock->ovpn = peer->ovpn; - netdev_hold(peer->ovpn->dev, &ovpn_sock->dev_tracker, - GFP_KERNEL); - } - - rcu_assign_sk_user_data(sk, ovpn_sock); sock_release: release_sock(sk); return ovpn_sock; diff --git a/drivers/net/ovpn/tcp.c b/drivers/net/ovpn/tcp.c index 0d7f30360d87..e078f9b39122 100644 --- a/drivers/net/ovpn/tcp.c +++ b/drivers/net/ovpn/tcp.c @@ -487,6 +487,7 @@ int ovpn_tcp_socket_attach(struct ovpn_socket *ovpn_sock, /* make sure no pre-existing encapsulation handler exists */ if (ovpn_sock->sk->sk_user_data) return -EBUSY; + rcu_assign_sk_user_data(ovpn_sock->sk, ovpn_sock); /* only a fully connected socket is expected. Connection should be * handled in userspace diff --git a/drivers/net/ovpn/udp.c b/drivers/net/ovpn/udp.c index d6a0f7a0b75d..272b535ecaad 100644 --- a/drivers/net/ovpn/udp.c +++ b/drivers/net/ovpn/udp.c @@ -386,6 +386,7 @@ int ovpn_udp_socket_attach(struct ovpn_socket *ovpn_sock, struct socket *sock, struct ovpn_priv *ovpn) { struct udp_tunnel_sock_cfg cfg = { + .sk_user_data = ovpn_sock, .encap_type = UDP_ENCAP_OVPNINUDP, .encap_rcv = ovpn_udp_encap_recv, .encap_destroy = ovpn_udp_encap_destroy, -- 2.52.0 _______________________________________________ Openvpn-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/openvpn-devel
